Non-embedding method for heavy metal stabilization using beef bone meal and blast media

ABSTRACT

Methods are disclosed for stabilizing a heavy metal in a heavy metal bearing paint residue to reduce leaching of the heavy metal from a waste subject to natural or induced leaching conditions by addition of environmentally safe, worker safe, and multi-media compatible stabilizing agent comprising beef bone meal. Beef bone meal is added to the blast media, and provides effective reduction of heavy metal content in waste leachate and effectively removes paint residue without causing visible embedding on the substrate surface, which meets the SSPC SP10 criteria for surface preparation prior to painting. The methods described herein may be used outside of or within an OSHA containment building or collection device. The resultant stabilized paint residue and spent blast media mixture is suitable for on-site reuse, off-site reuse, or disposal as RCRA non-hazardous waste.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/741,648, filed on Jul. 25, 2012. The entire teachings of the aboveapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Heavy metal bearing paint residue, and mixtures of heavy metal bearingpaint residue and spent paint removal blasting or abrasive media, may bedeemed “Hazardous Waste” by the United States Environmental ProtectionAgency (USEPA) pursuant to 40 C.F.R. Part 261 and also deemed hazardousunder similar regulations in other countries such as Japan, Switzerland,Germany, United Kingdom, Mexico, Australia, Canada, Taiwan, EuropeanCountries, India, and China, and deemed special waste within specificregions or states within those countries, if containing hazardous wasteregulatory method extraction fluid solution-soluble and/or sub-micronfilter-passing particle sized heavy metals such as; Arsenic (As), Silver(Ag), Barium (Ba), Lead (Pb), Cadmium (Cd), Chromium (Cr), Mercury (Hg),Selenium (Se), Copper (Cu), Zinc (Zn), and Antimony (Sb), above levelsdeemed hazardous by those country, regional and/or state regulators.

There exists a need for methods that reduce the solubility of mixedheavy metal bearing paint residue and spent blast media, such that theextract from these mixtures contains minimal concentrations of heavymetals that fall within limits deemed allowable by the U.S. and othercountries, enabling such mixtures to be classified as non-hazardouswaste.

The prior art has focused on reducing solubility of heavy metals, mostlylead, from paint residues by application of phosphate sources blendedwith Latex and silicates onto surfaces prior to blasting (Forrester U.S.Pat. No. 6,515,053 B1), application of certain acidulated calciumphosphates such as triple superphosphate and diammonium phosphateblended with blast media used for painted surface removal by airblasting (Forrester U.S. Pat. No. 6,186,939 B1), and post-paint removalblasting application of known heavy metal stabilizers such asphosphates, carbonates, cement, silicates, with or without mineralcomplexers, in accumulation tanks or waste piles after collection oraccumulation of the paint residue (Forrester U.S. Pat. No. 5,846,178,Forrester U.S. Pat. No. 5,722,928 and Forrester U.S. Pat. No. 5,536,899and references cited therein).

Several other methods have been investigated to decrease the amount ofheavy metal in industrial wastes. U.S. Pat. No. 5,202,033 describes anin-situ method for decreasing Pb Toxicity Characteristic LeachingProcedure (TCLP) leaching from solid waste using a combination of solidwaste additives and additional pH controlling agents from the source ofphosphate, carbonate, and sulfates. U.S. Pat. No. 5,037,479 discloses amethod for treating highly hazardous waste containing unacceptablelevels of TCLP Pb such as lead by mixing the solid waste with abuffering agent selected from the group consisting of magnesium oxide,magnesium hydroxide, reactive calcium carbonates and reactive magnesiumcarbonates with an additional agent which is either an acid or saltcontaining an anion from the group consisting of Triple Superphosphate(TSP), ammonium phosphate, diammonium phosphate, phosphoric acid, boricacid and metallic iron. U.S. Pat. No. 4,889,640 discloses a method andmixture from treating TCLP hazardous lead by mixing the solid waste withan agent selected from the group consisting of reactive calciumcarbonate, reactive magnesium carbonate and reactive calcium magnesiumcarbonate. U.S. Pat. No. 4,652,381 discloses a process for treatingindustrial wastewater contaminated with battery plant waste, such assulfuric acid and heavy metals by treating the waste waster with calciumcarbonate, calcium sulfate, calcium hydroxide to complete a separationof the heavy metals. Recently, calcium phosphates have been investigated(Forrester US 2012/0220810).

SUMMARY OF THE INVENTION

The present invention relates to methods for stabilizing a heavy metalin a heavy metal-containing paint residue to reduce leaching of theheavy metal when the paint residue is generated into paint waste andexposed to natural or induced leaching conditions. The method comprisescontacting a heavy metal-containing paint residue that is painted on asubstrate with a mixture comprising paint removal blast media and astabilizing agent comprising beef bone meal in an amount effective toreduce leaching of the heavy metal to a non-hazardous level, therebyforming a stabilized paint waste and a blast-cleaned substrate. In themethods of the current invention, the blast-cleaned substrate is notvisibly embedded with stabilizing agent or paint removal blast media.

In some aspects of the invention, the methods described herein are usedin an OSHA containment structure, or alternately in a collection device,wherein the beef bone meal contacts the paint residue before, during orafter exposure of the paint residue to an exhaust air filtration system.

The methods of the present invention may be utilized with all blastremoval techniques, including pressurized pot blasting or venturi-typepickup. In some aspects of the invention, the beef bone meal stabilizingagent is exposed to the paint residue as a mixture with blast media,which comprises dry blasting media, semi-wet sponge blasting media, orhigh pressure water. Dry blasting media used in the invention is drypowder, dry granule, or alternately a slurried mixture.

The methods of the present invention generate a stabilized paint waste,which in some embodiments of the invention, comprises heavy metalcontaining solid phase mineral, for example Pb₃(PO₄)₂, exhibiting lowtoxicity and low solubility under natural or induced leachingconditions. The solid phase mineral meets the criteria for resistance toleaching under Toxicity Characteristic Leaching Procedure (TCLP),Synthetic Precipitation Leaching Procedure (SPLP), California WasteExtraction Test (CALWET), Multiple Extraction Procedure (MEP) otherprotocols.

In some aspects of the invention, the resultant blast-cleaned substrateis compatible with subsequent application or paint surface cleaners,primers and paints.

The preferred stabilizer for lead bearing paint and spent media is 16 to200 US Sieve and preferably 30 to 100 US Sieve sized steamed beef bonemeal. In some aspects of the invention, the beef bone meal may be mixedwith an additive, wherein the additive comprises up to 50% by weight ofthe beef bone meal and additive blend. The additive comprises fish bonemeal, pork bone meal, crushed and milled phosphate rock ore, calciumphosphate sources such as single superphosphate, triple superphosphate,dicalcium phosphate, dicalcium phosphate dihydrate powder, monocalciumphosphate, and tricalcium phosphate for substitution of Pb into calciumphosphate apatite minerals, provided that the additive combined with thebeef bone meal does not cause any visual embedding into the substrate tobe blast-cleaned. In alternate embodiments of the invention, the beefbone meal may be mixed with an additive to create a blend, wherein theadditive comprises up to 50% by weight of the blend, for projects inwhich the Society for Protective Coatings (SSPC) standard ofnon-embedment is not established as a project criterion.

In an alternate embodiment of the invention, the methods herein relateto stabilizing a heavy-metal containing paint residue by contacting amixture of the paint residue and blast media with beef bone meal in anamount effective to reduce leaching of the heavy metal to anon-hazardous level.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings.

FIG. 1 is a photograph of a bolt at the Queets River Bridge blastingproject. After removal of paint utilizing Green Diamond Sand Productblast media and beef bone meal as described in the present invention, novisible embedding was observed.

FIG. 2 is a photograph of a section of the Queets River Bridge. Afterremoval of paint utilizing Green Diamond Sand Product blast media andbeef bone meal as described in the present invention, no visibleembedding was observed.

FIG. 3 is a photograph of a section of the Hood River Bridge. Afterremoval of paint utilizing Green Diamond Sand Product blast media andMonodicalcium Phosphate (MDCP), visible embedding was observed, whichappears as light-toned dots on the bridge surface.

DEFINITIONS

As used herein, a “heavy metal-containing paint residue” is a residue,optionally in chip, powder, flake or coating form that contains one ormore heavy metals such as arsenic, silver, barium, lead, cadmium,chromium, mercury, selenium, copper, zinc, antimony in any oxidationstate, including zero (e.g., Ag(0)).

“Induced leaching conditions” as used herein, means conditions such asmoisture content, pH, and temperature that mimic natural leachingconditions such as rain or acid rain observed in the environment orobserved in a real setting like a landfill. Induced leaching conditionscan be those implemented by country regulations, such as but not limitedto Toxicity Characteristic Leaching Procedure (TCLP), SyntheticPrecipitation Leaching Procedure (SPLP), California Waste ExtractionTest (CALWET), Multiple Extraction Procedure (MEP) and the like.

The term “stabilizing”, as in “stabilizing a heavy metal”, meansconverting the heavy metal into an insoluble mineral form. An effect ofstabilizing or stabilization of a heavy metal is that the amount ofheavy metal that leaches into an environment during natural or inducedleaching conditions is lowered. “Reduction of leaching”, or “reducedleaching” or “reducing leaching” and the like refer to decreasing theconcentration or the overall molar or mass quantities of a heavy metalthat is released into the environment during natural or induced leachingconditions.

As used herein, “paint waste” is paint residue intended for disposal.Paint waste can be generated from a paint removal method like blasting,or it can be a supply remaining from a painting project, or it caninclude flakes or chips that have come off of a substrate naturallywithout a paint removal method. Paint waste can comprise a variety ofcomponents, including pigments, sealants, polymers and heavy metals. A“stabilized paint waste” is a paint waste in which the heavy metals havebeen converted to an insoluble mineral form, optionally through contactwith a stabilizing agent.

“Spent paint removal blast media” includes blast media that has beenused in a paint removal process. Optionally, spent paint removal blastmedia comprises paint waste.

“Dusting” as used herein, refers to methods that generate smallparticulate matter visible to the naked eye in the course of blastcleaning a substrate. Non-dusting methods generate no visible amount ofparticulate emission from a point or line source.

A “non-hazardous level” means a level, for example, a concentrationlevel of a heavy metal, which is classified as non-hazardous oralternately non-toxic by a specific protocol as set forth by alaw-making body. As described herein, different countries maintaindifferent standards for non-hazardous waste, and also implementdifferent tests to measure hazardous or toxic content. As used herein, a“non-hazardous level” refers to the standards defined by the laws ofcountries including, but not limited to The United States, Canada,Mexico, Taiwan, China, Thailand, Japan, Hong Kong, Philippines,Australia, New Zealand, India, Brazil, the countries of Central andSouth America and the countries of the European Union.

“pH neutral” as used herein, refers to a material having a pH that isneither acidic nor basic, and is about 7.0.

The term “water insoluble” means a material having little to nosolubility in water; for example having no solubility below 5 grams ofcompound per 100 mL of deionized water at standard temperature andpressure (STP), wherein STP is 0.986 atm and 25° C.

The term “grind suitable” means a phosphate or another composition thatcan be ground with conventional grinding devices such as hammer mill orgear mill.

The terms “low settling” or alternately “low sifting” arecharacteristics of a composition that has little amount of compound thatsettles to the bottom of a bag or container during transport. Therefore,a composition that is “low settling” or “low sifting” remains relativelyuniform in concentration relative to the depth of a container whenplaced into a blasting pot or container.

DETAILED DESCRIPTION OF THE INVENTION

A description of example embodiments of the invention follows.

The present invention discloses a heavy metal bearing mixed paintresidue and spent paint removal media regulatory test extract heavymetal content solubility reduction method by contact of heavy metalbearing paint with a pre-blend of blast removal media and heavy metalstabilizers, where the pre-blend mixture is engineered for optimalperformance for a given paint removal project. The stabilizers arespecifically engineered and improved over existing pre-blendedstabilizers and blast media, given that this new pre-blended media andstabilizer method uses only environmental-safe, worker-safe, non-toxic,substrate compatible, and multi-media compatible stabilizers, suitablefor blending with dry blasting media, semi-wet sponge blast media, andhigh pressure water paint blast systems. It has been observed by theinventor that current heavy metal control and abatement systems usedworldwide at paint removal projects are not capable of collecting 100%of the newly generated stabilizer and paint blend, and thus the existingtechnologies are lacking in production of environmental and workerexposure safe resultant minerals and molecules that are also capable ofbeing used with the dry and wet abrasive removal techniques used bypaint removal and collection contractors.

The present invention relates to methods for stabilizing a heavy metalin a heavy metal-containing paint residue to reduce leaching of heavymetals from paint waste, comprising contacting a paint residue on asubstrate with a mixture of blast media and stabilization agent, therebyforming stabilized paint waste and a blast-cleaned substrate. Thestabilizing agent used in the present invention comprises beef bone mealand is non-dusting and adhere to the Society for Protective Coatings(SSPC) industry standard of zero visual embedding in the substrate. Inalternate embodiments of the invention, the methods described hereinstabilize a heavy metal in a mixture of heavy metal-containing paintresidue and spent paint removal blast media by contacting the mixedmedia with a stabilization agent comprising beef bone meal.

Previously invented methods failed to recognize the importance ofapplying a blended mixture of paint removal media and paint residuestabilizer with or without mineral complexing agents that are (1)engineered to be safe to the environment and biological communitieseither outside of or inside the painted structure OSHA containmentbuilding, safe to workers with regard to inhalation, ingestion, anddermal contact, non-toxic, and compatible with painted surfacesubstrate, (2) multi-media compatible and thus suitable for blendingwith dry blasting media, semi-wet sponge blast media, and high pressurewater paint blast systems, (3) of a certain density and physicalgeometry that allows for pre-blending with common blast media such asCoarse Black Beauty Blast Media or Green Diamond Sand Products, miningwaste and mining tailings, such that the pre-blend of stabilizer withblast media remains uniform and non-separated from production topackaging, to shipment, and finally to delivery, (4) not cause embeddingor residual adhesion of stabilizer onto the steel substrate lead paintedsurface, (5) form minimal dust during blasting from the stabilizer andmedia combination pre-blend, and (6) have low to no physical cementingcharacteristic. This last characteristic is a significant problem withthe currently commercially available Blastox product. (The TDJ Group,Inc.) Blastox has a lime and silicate water hydroscopic and cementingnature if wetted and/or allowed to attract moisture during storage anduse of the pre-blend and post use collection and storage prior todisposal. Further, Blastox and other current blasting techniques used toremove paint residue suffer from the disadvantage that their fine smallparticulate lime and silicate particles cause visible dust and adhere tosteel surfaces on blasting. This leaves small amounts of particles onthe surface of the substrate after blast cleaning Blast media andstabilizing agents used to sequester heavy metals also become visiblyembedded in the substrate from which paint is removed. The Society forProtective Coatings (SSPC) has implemented a standard whereby thesubstrate must be free of naked eye observable surface particles ofstabilizer or paint prior to priming or painting a substrate.

There is a need in the art for a method to concurrently remove heavymetal-containing paint from substrates while stabilizing the heavy-metalcontaining paint residue spent blast paint removal media. Further, sucha method must operate without causing visual embedding of a stabilizingagent or blast media into the substrate from which paint is beingremoved. The methods of the present invention presented herein addressand overcome these previous limitations and disadvantages in blastingtechnologies.

The present invention provides a method of reducing the solubility ofmixed heavy metal bearing paint residue and spent blast media. Paintresidue heavy metal solubility is controlled by the invention asmeasured under Toxicity Characteristic Leaching Procedure (TCLP),Synthetic Precipitation Leaching Procedure (SPLP; EPA Method 1312),California Waste Extraction Test (CALWET), Multiple Extraction procedure(MEP), rainwater and surface water leaching conditions, as well as underregulatory water extraction test conditions as defined by waste controlregulations in China, Thailand, Taiwan, Japan, Canada, UK, Mexico,Switzerland, Germany, Sweden, The Netherlands and under American NuclearStandards for sequential leaching of wastes by de-ionized water.

In the United States, any solid waste can be defined as Hazardous Wasteeither because it is listed in 40 C.F.R., Part 261 Subpart D, federalregulations adopted pursuant to the Resource Conservation and RecoveryAct (RCRA), or because it exhibits one or more of the characteristics ofa Hazardous Waste as defined in 40 C.F.R. Part 261, Subpart C. Thehazard characteristics defined under 40 C.F.R. Part 261 are: (1)ignitability, (2) corrosivity, (3) reactivity, and (4) toxicity astested under the Toxicity Characteristic Leaching Procedure (TCLP). 40C.F.R., Part 261.24(a), contains a list of heavy metals and theirassociated maximum allowable concentrations, as measured under the USEPAMethod 1311 leach test, TCLP. If a heavy metal, such as lead, exceedsits maximum allowable concentration of extract leaching from a solidwaste, when tested using the TCLP analysis as specified at 40 C.F.R.Part 261 Appendix 2, then the subject solid waste is classified as aRCRA Characteristic Hazardous Waste. The USEPA TCLP test, Method 1311,uses a dilute acetic acid either in de-ionized water (TCLP fluid 2) orin de-ionized water with a sodium hydroxide buffer (TCLP fluid 1). Bothextract methods attempt to simulate the leachate character from adecomposing trash landfill in which the solid waste being tested for isassumed to be disposed in and thus subject to rainwater and decomposingorganic matter leachate combination or an acetic acid leachingcondition. Wastes containing TCLP leachable heavy metals are currentlyclassified as hazardous waste due to the toxicity characteristic, if thelevel of TCLP analysis is above 0.2 to 100 milligrams per liter (mg/L)(or parts per million (ppm)) for specific heavy metals as defined under40 C.F.R. part 261.24. The TCLP test is designed to simulate aworst-case leaching situation or specifically a leaching environmenttypically found in the interior of an actively degrading municipallandfill. Such landfills normally are slightly acidic with a pH ofapproximately 5±0.5. Similarly, the SPLP test replaces acetic acid withdilute sulfuric and dilute nitric acid to simulate acid rain. MEPoperates by replacing the one 18-hour extract of TCPLP with tensequential extracts, which measures the long-term usability and stayingpower of the stabilizer used to reduce heavy metal extraction ability.

Countries outside of the US, such as Taiwan, Philippines and Canada,also use the TCLP test as a measure of leaching. Thailand also limitssolubility of Cu and Zn, as these are metals of concern to Thailandgroundwater. Switzerland and Japan regulate management of solid wastesby measuring heavy metals and salts as tested by a sequential leachingmethod using carbonated water simulating rainwater and de-ionized watersequential testing. Additionally, USEPA land disposal restrictionsprohibit the land disposal of solid waste leaching in excess of maximumallowable concentrations upon performance of the TCLP analysis. The landdisposal regulations require that hazardous wastes are treated until theheavy metals do not leach at levels from the solid waste at levels abovethe maximum allowable concentrations prior to placement in a surfaceimpoundment, waste pile, landfill or other land disposal unit as definedin 40 C.F.R. 260.10.

Suitable acetic acid leach tests include the USEPA SW-846 Manualdescribed Toxicity Characteristic Leaching Procedure (TCLP) andExtraction Procedure Toxicity Test (EP Tox), which is used in allCanadian Provinces except Quebec. Briefly, in a TCLP test, 100 grams ofwaste are tumbled with 2000 ml of dilute and buffered or non-bufferedacetic acid for 18 hours and then filtered through a 0.75 micron filterprior to nitric acid digestion and final ICP analyses for total“soluble” metals. The extract solution is made up from 5.7 ml of glacialacetic acid and 64.3 ml of 1.0 normal sodium hydroxide up to 1000 mldilution with reagent DI water.

Suitable deionized (DI) carbonated water leach tests include theJapanese leach test which tumbles 50 grams of composited waste sample in500 ml of water for 6 hours held at pH 5.8 to 6.3, followed bycentrifuge and 0.45 micron filtration prior to analyses. Anothersuitable distilled water CO₂ saturated method is the Swiss protocolusing 100 grams of cemented waste at 1 cm³ in two sequential water bathsof 2000 ml. The concentration of lead and salts are measured for eachbath and averaged together before comparison to the Swiss criteria.

Suitable citric acid leach tests include the California Waste ExtractionTest (CALWET), which is described in Title 22, Section 66700,“Environmental Health” of the California Health & Safety Code. Briefly,in a WET test, 50 grams of waste are tumbled in a 1000 ml tumbler with500 grams of sodium citrate solution for a period of 48 hours. Theconcentration of leached lead is then analyzed by Inductively-CoupledPlasma (ICP) after filtration of a 100 ml aliquot from the tumblerthrough a 45 micron glass bead filter.

Heavy metals stabilized by the methods of the present invention includearsenic, silver, barium, lead, cadmium, chromium, mercury, selenium,copper, zinc, antimony and combinations thereof. Such heavy metals oftencomprise from about 0.5% to about 40% by weight of the pain residue,alternately as low as about 20 ppm to as high as about 800,000 ppm ofthe paint residue.

Environmental regulations throughout the world, such as USEPAregulations written under Resource Conservation Recovery Act (RCRA)(available at epa.gov/rcraonline) and Comprehensive EnvironmentalResponse, Compensation, and Liability Act (CERCLA) mandate (U.S.C. Title42), require heavy metal bearing waste, heavy metal bearing contaminatedsoils, and materials producers to manage such materials and wastes in amanner safe to the environment and to human health. In response to theseregulations, environmental engineers and scientists have developednumerous means to control heavy metals, mostly through chemicalapplications which convert the solubility of the material and wastecharacter to a less soluble form, such that the waste passes leachtests. This enables the wastes to be either reused on-site, or disposedat local landfills without necessitating expensive hazardous wastedisposal landfills or regional Treatment Storage and Disposal Facilities(TSDF) designed to provide metals stabilization. Historically, theprimary focus of scientists has been reducing solubility of heavy metalssuch as lead, cadmium, chromium, arsenic and mercury, as these were andcontinue to be the most significant mass of metal contamination insoils. Major lead sources, on the other hand, include materials such aspaint residues, cleanup site wastes such as battery acids, and slagwastes from smelters and incinerators.

There exists a demand for improved and less costly control methods ofheavy metals from paint residue removal and recovery projects thatallows for stabilization of heavy metals in paint residue and spentblast media into non-hazardous waste or materials that are stable,environmental-safe, worker-safe, non-toxic, substrate compatible, andmulti-media compatible, and suitable for blending with dry blastingmedia, semi-wet sponge blast media, and high pressure water paint blastsystems. The subject method allows for stabilized paint residue andspent media production and handling either outside of or within thepaint residue OSHA enclosure after residue removal from the structureand/or within devices used to collect residue from the OSHA containerand before the discharge of the residues into accumulation containers.

In some aspects of the invention, the stabilizing agent is blended withblast media and applied to a painted substrate as a mixture during blasttreatment of the substrate. Suitable blasting methods and instrumentsfor use with the present invention include pressurized pot blasting,venturi blasting, and other methods of vacuum collection of stabilizedblast media and lead paint mixture. The stabilizing agent used in theblasting methods described herein does not cause dusting or embedding inthe substrate.

In alternate aspects of the invention, the stabilizing agent comprisesbeef bone meal and is used in other methods of on-site stabilization,including as a paint additive, as an in-tank dry stabilizer additive, oras an OSHA containment unit floor spreading stabilizer additive.

The subject pre-mixed, non-separating stabilizer and blast media methodallows for stabilized paint residue and spent paint removal mediaproduction and handling either outside of or within the paint residueOSHA enclosure after residue removal from the structure and/or withindevices used to collect residue from the OSHA container and before thedischarge of the residues into accumulation containers.

The methods described herein are environmentally benign in that themethods reduce the solubility of the heavy metals contained in paintresidue, and therefore diminish the amount of heavy metal that isleached into the environment during blast cleaning of a substrate orduring disposal of paint waste. Similarly, the methods described hereinare benign to human health, in that the stabilizing agents reduce theamount of heavy metal to which a worker is exposed during blasting.Further, beef bone meal, as described herein, does not generate dust.Blasting small particles causes significant dusting, which is notdesirable for blasting contractors due to concern for worker safety,environmental safety, and compliance with state and local laws andordinances.

In some embodiments of the invention, the methods described hereinremove and stabilize heavy-metal bearing paint from a substrate andfurther prepare the substrate for subsequent proofing, coating orpainting. Accordingly, the methods of the present invention do not causevisual embedding or residual adhesion of either the stabilizer or theblast media on the surface of the substrate.

The stabilizing agent for use in the present invention comprises beefbone meal. In some aspects of the invention, the beef bone meal iscombined with complexers containing chlorides. Without being bound totheory, complexers containing chloride allow for formation ofchloropyromorphite apatite mineral. Such a lead chloropyromorphite has aK_(sp) in water of 10E-92 versus a K_(sp) of 10E-20 for lead phosphate.

In further aspects of the invention, for projects in which the SSPCstandard of non-embedment is not a criterion, or for which a less-strictnon-embedment criterion is established, beef bone meal can be combinedwith inexpensive stabilizers such as phosphate rock and calciumphosphate sources such as monocalcium phosphate, single superphosphate,triple superphosphate, dicalcium phosphate, dicalcium phosphatedihydrate powder, monocalcium phosphate, and tricalcium phosphate forsubstitution of Pb into calcium phosphate apatite minerals. The additivecan comprise up to 50% by weight of the blend of beef bone meal andadditive.

In yet further aspects of the present invention, beef bone meal can becombined with an additive suitable for the stabilization of lead andother heavy metals, wherein the mixture of additive and beef bone mealmeets the non-embedment project criterion established by the SSPC.Certain additives, such as about 16 to about 200 US Sieve, oralternately about 30 to about 100 US Sieve sized steamed pork bone meal,fishbone meal, phosphate rock, or calcium phosphate stabilizeradditives, may be used in up to 50% by weight blend with the beef bonemeal for TCLP reduction of lead concentration and still meet thenon-embedment requirement. In some aspects of the invention, beef bonemeal in 50% blend with phosphate rock or pork bone meal utilizing aventuri vacuum pickup method with a lower pressure blasting nozzle on alaboratory scale does not cause visual embedment of the substrate. Beefbone meal, pork bone meal, fishbone meal, phosphate rock and calciumphosphates have the unique capability to be applied as a dry powder, drygranular, or fine colloidal slurry mixture additive that will remainsuspended in solution and convey uniformly with pressurized pots andmedia venturi pickup blast methods. This advantage is due to the minimalwater solubility of bone and ore phosphates and calcium phosphates,which prevents these materials from exothermic curing in wetted media.Such exothermic curing occurs with wetting or semi-wetting of alternatetechnologies such as Blastox calcium silicates and calcium oxides, bothof which are highly water soluble and highly hydroscopic and reactive.The most significant advantage with production of lead substituted boneand ore apatites and calcium phosphate minerals in paint residue is thatthe solubility constant, and hence leachability and bioavailability, aregreatly reduced in this true apatite form at K_(sp) 10E-92, as comparedto the simple lead-silicate and lead-oxide minerals forms at K_(sp)values greater than 10E-5 from Blastox type amended solid media. Mostpreferably, the stabilizing agent is beef bone meal. Beef bone meal hasa lower protein and moisture content than other bone meals such as porkor fish. Low protein and moisture content is particularly advantageousbecause bone meals having high moisture and protein content leaveresidue on the substrate, and thus may fail the SSPC industryrequirement of non-embedment and non-attached media stabilizer prior tothe subsequent application of paint.

In some aspects of the invention, the bone meal is from about 200 meshto about ¼ inch (0.635 cm) diameter size particle, and in some aspectsof the invention, the bone meal is powder, granulated, or flake. In apreferred embodiment of the invention, the beef bone meal that is mixedwith the blast media is in ¼ inch (0.635 cm) flake shape. Without beingbound by theory, the preferred ¼ inch flake beef bone meal isparticularly advantageous in that it shatters on impact with thesubstrate, opening more phosphate surface area for precipitation and ionexchange, which effectively stabilizes the heavy metals in the paintresidue or the mixed paint residue and spent blast paint removal media.The dynamic velocity of the bone meal stabilizing agent is a result ofpressurized air mixed with, for example, a pot source of blast media andstabilizer blend. Utilizing bone meal in blasting methods improves itsTCLP control ability.

The shattering effect is advantageous because the bone meal remainsintact until shattering on impact with the substrate. Thus, the methodsof the present invention limit dusting at the blast nozzle and allow thebone fragment to remain low-sifting and low-settling with blast media inthe blast pot container.

The beef bone meal used in the present invention is non-separating,i.e., the stabilizing agent remains integral within the blast media,which enables a uniform and steady-state dosage of the stabilizing agentper unit of blast media, a feature necessary for reliable in-linestabilization. Beef bone meal is advantageous in that it is pH-neutral,water-insoluble, grind-suitable, non-sifting, non-settling, safe to bothenvironment and human worker, and an OSHA-DOT non-hazardous andnon-regulated material. Beef bone meal is steamed and crushed naturalbeef bone material. In some embodiments, beef bone meal means steamedbeef bone meal. Its hardness and brittle character allow it to behandled and blended with solid media without causing embedding uponblasting.

The form of beef bone meal, the dose rate and weight percent, and thecomposition of the blasting media can be selected and engineered foreach blasting environment and each type of paint residue compositionanticipated, such as lead, chromium, arsenic, copper, zinc orcombinations thereof.

In typical stabilization technologies, the dosage of the stabilizer isvery low, from 0.5% to 5% of the weight of blended blast media. Thus, itis very important that the stabilizer remain suspended within the solidblast media matrix, such that it is introduced into the blasted paintwaste at a uniform and steady-state manner, allowing for uniformdistribution of the stabilizer “seed” into the mixed media and residue.The weight percent of stabilizer used will be a stabilizer dose to wasteratio that has been determined by prior lab analyses as the minimumrequired to assure that the stabilized blend of residue and media meetsnon-hazardous waste criteria, for example, less than 5.0 ppm TCLP Pb inthe US, Taiwan, Philippines and Canada. There is a need for astabilizing agent that can be premixed with blast media for heavy-metalcontaining paint removal, wherein the stabilizing agent remainsuniformly distributed in the media and does not cause separation of themixture. Such a mixture would be useful for the production and handlingof stabilized heavy metal-containing paint residue and spent paintremoval media, and would be utilized either outside of or within a paintresidue OSHA enclosure before the residues are discharged intoaccumulation containers.

In some aspects of the invention, the beef bone meal is pre-mixed withthe blasting media. Methods by which the stabilizing agent and theblasting media are blended together include, but are not limited to ballmill, cone blending, tumbling, and slurry cycling. Typical blast mediafor use in the methods of the present invention include but are notlimited to garnet, Green Diamond Sand that comprises mine tailingcrushed rock, Black Beauty comprising coal slag, shell comprisingnatural ground shells of nuts and shellfish, sand, sponge, steel shot,rubber or high pressure water. In preferred embodiments of theinvention, the stabilization agent is about 0.5 to about 5% by weight ofthe composition as mixed with the blasting media. In preferredembodiments the stabilization agent is about 1 to about 2% by weight ofthe composition. In more preferred embodiment of the invention, themixture of stabilizing agent in blasting media is 2% beef bone meal inGreen Diamond Sand.

When heavy metals in paint residue such as lead come into contact withthe stabilizing agent and blended media with sufficient reaction timeand energy, apatite minerals with low water solubility form, such as aPb, Cr and As substituted hydroxyapatites, apatite Pb₃(PO₄)₂, and in thecase of beef bone meal combined with complexers, chloropyromorphite.Through substitution or surface bonding, these minerals form at thepoint of media and stabilizer contact with painted surfaces, and theseapatite minerals are less soluble than the heavy metal element ormolecule originally in the paint residue. There exist several thousandpossible mineral low-solubility combinations possibly formed given thepaint residue composition and possible stabilizer additives identified.Certain combinations of beef bone meal and additives may provide forlong-term stabilization and passage of leach tests beyond thatregulated, and thus be more suited to paint residues intended for reuseor land application. The present invention provides a multitude ofstabilizer options for the stabilization design engineer, which can betested for final recipe solubility under the various leach tests ofinterest.

Although the beef bone meal is the preferred embodiment, examples ofpossible additive stabilizing and/or complexing agents include, but arenot limited to, chlorides, iron, aluminum, ferric and ferrous sulfates,aluminum sulfate, flocculants, coagulants, nuclei particulates, ligands,cement kiln dust, lime kiln dust, sulfides, iron, silicates, phosphatefeeds, phosphate fertilizers, phosphate rock, pulverized phosphate rock,calcium orthophosphates, trisodium phosphates, calcium oxide(quicklime), dolomitic quicklime, natural phosphates, phosphoric acids,dry process technical grade phosphoric acid, wet process greenphosphoric acid, wet process amber phosphoric acid, black phosphoricacid, merchant grade phosphoric acid, aluminum finishing phosphoric andsulfuric acid solution, hypophosphoric acid, metaphosphoric acid,hexametaphosphate, tertrapotassium polyphosphate, polyphosphates,trisodium phosphates, pyrophosphoric acid, fishbone phosphate, animalbone phosphate, herring meal, bone meal, phosphorites, and combinationsthereof. Salts of phosphoric acid can be used and are preferably alkalimetal salts such as, but not limited to, trisodium phosphate, dicalciumphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate,tripotassium phosphate, dipotassium hydrogen phosphate, potassiumdihydrogen phosphate, trilithium phosphate, dilithium hydrogenphosphate, lithium dihydrogen phosphate or mixtures thereof.

The amounts of beef bone meal and optional additional agents andcomplexing additive combinations used, according to the method ofinvention, depend on various factors including desired solubilityreduction potential. Such solubility may be determined to be, forexample, less than 5.0 ppm or 0.75 ppm TCLP Pb as required under 40 CFRPart 261.24 or 40 CFR part 268 LDR disposal limitation for land disposedstabilized paint residue and media mixtures. In alternate aspects of theinvention, the stabilizing agent and dosage is selected based upondesired mineral toxicity, for example less than 50% lethal dose whenexposed to a batch aquatic toxicity test using fathead minnows under theWashington state Department of Ecology (WADOE) toxicity regulations. Inyet another aspect of the invention, the stabilizing agent and dosagethereof is based upon desired mineral formation relating totoxicological and site environmental control objectives, for examplelead pyromorphites, chloropyromorphite, corkite, or plumbogummite. Theforegoing does not preclude higher or lower pre-blend dose ofstabilizing agents or combinations of stabilizers and complexing agents.

The examples below are merely illustrative of this invention and are notintended to limit it thereby in any way.

EXAMPLES Example 1

Green Diamond Sand Product (GDSP) blast media combined with 2% by weightsteamed beef bone meal screened to less than ¼ inch diameter(FESI-BOND-X1) was utilized in paint removal from the Queets RiverBridge. The reduction in lead in the paint residue after treatment withthe amended blast media is significant and meets TCLP standards. FIGS. 1and 2 are photographs from this series of tests that demonstrate novisual embedding at the Queets River Bridge.

concentration in concentration in paint residue paint residue afterprior to blast treatment with analyte treatment unit FESI-BOND unit TCLPArsenic <0.05 mg/L <0.05 mg/L TCLP Barium 0.381 mg/L 0.287 mg/L TCLPCadmium 0.020 mg/L 0.015 mg/L TCLP 0.062 mg/L 0.063 mg/L Chromium TCLPLead 37.2 mg/L 0.50 mg/L TCLP Selenium <0.08 mg/L <0.08 mg/L TCLP Silver<0.007 mg/L <0.007 mg/L TCLP Mercury <0.0002 mg/L <0.0002 mg/L

Pilot tests using GDSP showed visual embedment, sifting, settling anddusting with Monodicalcium Phosphate (MDCP), tricalcium phosphate ormonocalcium phosphate as triple superphosphate as stabilizing agent.FIG. 3 is a picture of the Hood River Bridge after blasting with GreenDiamond Sand Product and MDCP blend (FESI Dry-W) and shows significantvisual embedding in the substrate. Beef bone meal under analogousconditions demonstrated no visual embedding, no sifting, no settling,and no dusting.

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

The teachings of all patents, published applications and referencescited herein are incorporated by reference in their entirety.

What is claimed is:
 1. A method for stabilizing a heavy metal in a heavymetal-containing paint residue to reduce leaching of the heavy metaltherefrom when said paint residue is generated into paint waste andexposed to natural or induced leaching conditions, comprising:contacting a heavy metal-containing paint residue that is painted on asubstrate with a mixture comprising paint removal blast media and astabilizing agent comprising beef bone meal in an amount effective toreduce leaching of the heavy metal to a non-hazardous level, therebyforming a stabilized paint waste and a blast-cleaned substrate; whereinthe blast-cleaned substrate is not visibly embedded with stabilizingagent and paint removal blast media.
 2. The method of claim 1, whereinthe paint residue is contacted with the mixture within an OccupationalSafety and Health Administration (OSHA) containment structure.
 3. Themethod of claim 1, wherein the paint residue is contacted with themixture within a collection device comprising an exhaust air filtrationcyclone or baghouse.
 4. The method of claim 3, wherein contacting thepaint residue with the mixture occurs prior to exposure of the paintresidue to an exhaust air filtration cyclone or baghouse.
 5. The methodof claim 1, wherein the paint residue is contacted with the mixturewithin a vacuum collection device after exposure of the paint residue toan exhaust air filtration cyclone or baghouse and before the dischargeof the paint residue to an accumulation tank.
 6. The method of claim 1,wherein the paint residue is contacted with the mixture within a vacuumcollection device after exposure of the paint residue to an exhaust airfiltration cyclone or baghouse and during the discharge of the paintresidue to an accumulation tank.
 7. The method of claim 1, wherein thepaint residue is contacted with the mixture within a vacuum collectiondevice during exposure of the paint residue to an exhaust air filtrationcyclone or baghouse.
 8. The method of claim 1, wherein the stabilizingagent is used in pressurized blast pots or a venturi-type pickupapparatus.
 9. The method of claim 1, wherein paint removal blast mediais a dry blasting media, a semi-wet sponge blasting media or highpressure water.
 10. The method of claim 1, wherein the stabilizing agentis in the form of a dry powder, a dry granule, or as a slurried mixture.11. The method of claim 3, wherein the mixture comprising paint removalblast media and stabilizing agent comprises beef bone meal at 2% byweight in mining tailing crushed rock.
 12. The method of claim 1,wherein the stabilized paint waste comprises a heavy-metal containingsolid phase mineral exhibiting low toxicity and low solubility undernatural or induced leaching conditions.
 13. The method of claim 12,wherein the solid phase mineral is Pb₃(PO₄)₂.
 14. The method of claim13, wherein the mineral has low solubility in water and simulatedrainwater extract and meets the criteria for resistance to leachingunder SPLP leaching test USEPA method
 1310. 15. The method of claim 1,wherein the blast-cleaned substrate is compatible with subsequentapplication of at least one of paint surface cleaner, primer and paint.16. The method of claim 1, wherein the stabilizing agent stabilizesheavy metals and reduces leaching of heavy metals in paint residue,spent paint removal blast media, substrates and residual airborne ordeposited dust.
 17. The method of claim 1, wherein the resultant paintwaste and mixed spent paint removal blast media and stabilizing agentdoes not classify as characteristic hazardous waste according to theToxicity Characteristic Leaching Procedure, Test Method
 1311. 18. Themethod of claim 1, wherein the mixture further comprises bone meal, porkbone meal, fish bone meal, fishbone, phosphate rock, calcium phosphates,Portland Cement, cement kiln dust, lime kiln dust, lime, silicates,sulfides, iron, quicklime, phosphate complexers chlorides, iron and/oraluminum; wet process amber phosphoric acid, wet process greenphosphoric acid, coproduct phosphoric acid solution from aluminumpolishing, technical grade phosphoric acid, hexametaphosphate,polyphosphate, calcium orthophosphate, superphosphates, triplesuperphosphates, single superphosphate, ordinary superphosphates, cropproduction phosphates, phosphate feeds, phosphate fertilizers,tetrapotassium polyphosphate, monocalcium phosphate, monoammoniaphosphate, diammonium phosphate, dicalcium phosphate, dicalciumphosphate dihydrate powder, tricalcium phosphate, trisodium phosphate,salts of phosphoric acid, or combinations thereof.
 19. A method forstabilizing a heavy metal in mixed heavy metal-containing paint residueand spent paint removal blast media to reduce leaching of the heavymetal under natural or induced leaching conditions, comprising:contacting mixed heavy metal-containing paint residue and paint removalblast media with beef bone meal in an amount effective to reduceleaching of the heavy metal to a non-hazardous level, thereby forming astabilized waste.
 20. A method of reducing the solubility of mixed heavymetal bearing paint residue and spent paint removal media and meetingthe Society for Protective Coatings standard of no-visual embedding ofstabilizer or media particles on blast cleaned substrate, comprisingcontacting the mixed paint residue and spent paint removal media with atleast a stabilizing agent comprising beef bone meal in an amounteffective in reducing the leaching of heavy metal to a level no morethan non-hazardous levels as determined in an EPA TCLP test, performedon the stabilized material or waste, as set forth in the FederalRegister, vol. 55, no. 126, pp. 26985-26998 (Jun. 29, 1990), andselecting the shape and size of the beef bone meal such that theresulting stabilizer and blast media meets project criteria of nonaked-eye observable substrate embedding.